The present invention relates to a rotation detecting apparatus and, in particular, to an apparatus suitable for detecting an amount of steering angle change, as one of parameters for controlling a power steering mechanism which assists a steering operation of an automobile in power.
Heretofore, the steering angle change in the power steering mechanism has been detected by means of a detector which is mounted on a steering column shaft or in the vicinity of a steering wheel and converts the steering angle change to an electric signal, or by means of converting the torsional stress of a torsion bar of a control valve (servo valve) to an electric signal, the valve controlling the supply of power fluid to a power cylinder in cooperation with the steering wheel. However, such detecting means cannot give effect to faithfully detect a subtle change of an actual steering angle of the wheel and an amount of power assistance for the power servo mechanism because it is adversely effected by the stress of the steering column shaft, the universal joint, the torsion bar of the control valve and the like when the rotation of the steering wheel by a manual operation is transmitted to the power steering mechanism. Additionally, it is very difficult in practical application provide a conventional detecting means as described above in the power steering mechanism because it is complicated in construction.